1. Technical Field
The present invention relates generally to an in-tank fuel pump apparatus having a fuel pump and a fuel filter disposed within a fuel tank which may be employed in fuel supply systems for automotive vehicles. More particularly, the invention is directed to an improved structure of an in-tank fuel pump for achieving electrostatic dissipation.
2. Background of Related Art
Japanese Patent First Publication No. 3-105055 assigned to the same assignee as that of this application teaches a fuel supply apparatus for automotive vehicles. The fuel supply apparatus includes a fuel pump disposed within a fuel tank. The fuel pump discharges fuel out of the fuel tank through a discharge pipe and sprays it into combustion chambers of an engine through fuel injectors. An excess of the fuel is returned to a sub-tank through a return pipe.
The above prior art fuel supply apparatus, however, encounters the following drawback. Mounting members for component parts such as the fuel pump and so forth are made of a metallic material. Screws and clips are used to fix the component parts. The assembling of the apparatus, thus, requires a great number of surface treatment processes for brazed and welded portions, resulting in increased total manufacturing costs of the apparatus.
Further, a technique is well known in the art wherein a fuel pump, a pressure regulator, and a fuel filter are disposed within a fuel tank to simplify the structure of a return pipe arranged outside the fuel tank for returning the fuel to the fuel tank through the fuel filter. Such a fuel supply system has disadvantages that friction between a filter element and the fuel passing through the filter element produces electrostatic charges, which may cause resin-made parts to be broken or damaged. In order to dissipate the electrostatic charges, the use of an earth circuit is preferred, but undesirably increases component parts.
Another type of fuel supply system is known in the art which returns through a pressure regulator part of fuel discharged from a fuel pump to a fuel tank. In this system, only fuel to be consumed in an engine passes through a fuel filter, while most of the fuel discharged from the fuel pump is returned to the fuel tank through the pressure regulator. Specifically, most of the fuel returned to the fuel tank does not pass through the fuel filter, thereby causing a pump filter to be blocked or friction to occur in the fuel tank. Further, the use of a fuel filter in a return pipe of a pressure regulator is proposed, but this technique has the disadvantage that foreign substances existing in a fuel passage line extending from an outlet port of the fuel pump to an inlet port of the pressure regulator may enter the pressure regulator, causing friction to occur in the pressure regulator resulting in wear or breakage of the pressure regulator.